The present invention pertains generally to lasers and more particularly to excimer lasers.
Laser oscillations in KrCl were first achieved in electron beam pumped devices by J. R. Murray and H. T. Powell, Appl. Phys. Letts. 29, 252 (1976). As disclosed by Murray and Powell supra, Cl.sub.2 was used as a halogen donor and laser oscillations obtained were near threshold level. Using prior art e-beam excited lasers, KrCl has not shown promise of becoming a useful coherent source of ultraviolet radiation due to its low output energy.
Ishchenko et al. have reported lasing in XeCl and low-energy lasing in KrCl with BCl.sub.3 as the halogen donor, as reported in Opt. Comm. 21, 30 (1977). Use of HCl as a halogen donor in an electric discharge system was thought to be untenable in view of the fact that the dissociation energy of HCl and the photon energy of KrCl lasers is within 0.02 eV of the .sup.3 P.sub.1 resonance trapped state of Kryton. Consequently, harpooning reactions: Kr.sub.M *+HCl.fwdarw.KrCl*+H, were thought to be inefficient due to the minimal amount of energy available from Kr.sub.M *. Consequently, the use of HCl as a halogen donor in an electric discharge KrCl laser was not attempted.
Furthermore, the use of prior art e-beam excited KrCl lasers, unknowingly, forms an initially large number of atomic and molecular ions such as Kr.sub.2.sup.+, Ar.sub.2.sup.+ and Ne.sub.2.sup.+ which absorb the 222 nm laser radiation, thereby impeding generation of a high energy lasing output. Formation of atomic and molecular ions in prior art e-beam excited discharges is unavoidable since the e-beam excited discharge functions by dissociating CL.sub.2 and ionizing the Kr gas by deposition of a large amount of energy in the active medium to form free Kr.sup.+ and Cl.sup.-, which interact to form KrCl. Consequently, a large number of Kr.sub.2.sup.+, Ar.sub.2.sup.+ and Ne.sub.2.sup.+ molecular ions are initially formed by the e-beam device which have an absorption spectrum which overlaps the 222 nm output frequency, resulting in low output lasing energies.